1. Field of the Invention
The present invention finds principal application in the field of passive solar energy systems. More particularly, the invention relates to a sensitive buoyant element check valve for use in solar energy systems which employ a thermosiphoning loop of liquid to convectively transfer heat.
2. Prior Art
With the dwindling supplies of fossil fuel and the accompanying increasing energy costs, extensive research efforts are being focused to harness solar radiation on a practical and economical scale. One type of device which shows promise in the field is a thermosiphon system, described in U.S. Pat. No. 4,137,964, issued to Bruce Shawn Buckley and in U.S. application Ser. No. 6,767, filed Jan. 26, 1979, by the same inventor, is now U.S. Pat. No. 4,245,617.
As disclosed in the above references, a "thermic diode" panel collects and stores the sun's radiant energy. The panel typically comprises a shallow rectangular box that is effectively divided into two chambers which are insulated from each other. The chambers are filled with a heat transport liquid, such as water, and are in open communication with each other at the bottom and at the top of the panel.
Solar radiation incident on the outer panel face will heat the water in the collector chamber. As the water expands it passes upwardly through the collector chamber and into the cooler storage chamber. Cooler water from the storage chamber, in turn, passes to the bottom of the warmer collector chamber.
If such a panel is used during the day to collect solar energy and store heat for nighttime use, reverse thermosiphoning should be avoided to prevent energy loss. The above references disclose several types of control devices for preventing same. In particular, the U.S. Pat. No. 4,137,964 patent teached the use of a ball float valve which is temperature-dependent.
The present invention, however, provides an inexpensive temperature-dependent, double acting valve which will function at low pressure differences, exhibit low pressure drops, and prevent reverse thermosiphoning under normal conditions.